In electronics, an optocoupler, also known as an opto-isolator photocoupler, or optical isolator, is an electronic device that transfers electrical signals using light waves to provide coupling with electrical isolation between the input and output of the optocoupler. The main purpose of an optocoupler is to prevent high voltages or rapidly changing voltages on one side of the optocoupler from damaging components or distorting transmissions on the other side of the optocoupler. By way of example, some commercially available optocouplers are designed to withstand input-to-output voltages of up to 10 kV and voltage transients with speeds up to 10 kV/usec.
In an optocoupler, input and output sides of the device are connected with a beam of light (typically falling in the infrared or near-infrared spectrum) modulated by input currents proportional to the electrical signals input to the device. The optocoupler transforms the input electrical signals into light, sends the corresponding light signals across a dielectric channel, captures the transmitted light signals on the output side of the optocoupler, and transforms the transmitted light signals back into output electric signals. Some optocouplers employ infrared or near-infrared light emitting diodes (LEDs) to transmit the light signals and photodetectors to detect the light signals and convert them into output electrical signals.
Some optocouplers include side-by-side closely matched photodetectors, where one the photodetectors is employed to monitor and stabilize the light output of the LED to reduce the effects of non-linearity, drift and aging of the LED, and the other photodetector is employed to generate output signals. See, for example, Avago Technologies™ “HCNR200 and HCNR201 High-Linearity Analog Optocouplers,” Dec. 10, 2011, the Data Sheet for which is filed on even date herewith in an accompanying Information Disclosure Statement, the entirety of which is hereby incorporated by reference herein.
Many commercially available optocouplers are provided in standard 8-pin dual in-line (DIP) or other standard format packages. While in such packages feedback control and modulation of the LEDs disposed therein on the basis of the detected light signals is often desirable, doing so may require a package that is larger and has more complicated circuitry than is desired. Among other things, what is needed is an optocoupler package having improved feedback control capabilities that is smaller and features less complicated feedback control circuitry.